反应详情

180 parts of a black crude 6-methoxy-3-acetylamino-aniline (prepared by the procedure of European Pat. No. 0,011,048, but with the addition of 10% of water before the hydrogenation and with an increase in the acetylation temperature to 20°-25° C., which resulted in less smooth reduction of the nitro groups and significantly lower selectivity in the monoacetylation), which, according to HPLC, contained, in addition to 124 parts of target product and 22 parts of 2,4-bisacetylamino-anisole, considerable amounts (about 30-35 parts) of unidentifiable byproducts and decomposition products formed by oxidation, were dissolved in 500 parts of methanol at 50° C. and, after the solution had been cooled to 20°-25° C., 100 parts of 30% strength hydrochloric acid were added dropwise in the course of 30 minutes, with stirring, and the mixture was then subsequently stirred for 1.5 hours. The product isolated by filtration on a suction filter after the mixture had been cooled to 0°-5° C. was washed twice with 100 parts of methanol each time and dried in vacuo. 144 parts of almost colorless 6-methoxy-3-acetylamino-aniline hydrochloride were obtained which, according to HPLC analysis, contained no organic impurities at all and had a purity, by diazotization, of 99.3%, corresponding to a yield of 96.8% of theory, based on 6-methoxy-3-acetylamino-aniline contained in the crude product.

1. temperaturewith an increase in the acetylation temperature to 20°-25° C.
2. customwhich resulted in less smooth reduction of the nitro groups and significantly lower selectivity in the monoacetylation), which
3. customformed by oxidation
4. temperatureafter the solution had been cooled to 20°-25° C.
5. stirringthe mixture was then subsequently stirred for 1.5 hours
6. customThe product isolated by filtration on a suction
7. filtrationfilter after the mixture
8. temperaturehad been cooled to 0°-5° C.
9. washwas washed twice with 100 parts of methanol each time
10. customdried in vacuo